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      <base href="https://bugs.freedesktop.org/" />
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        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - xlib.fallback occasionally incorrectly treats OVER as SOURCE"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=83896">83896</a>
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>chris@chris-wilson.co.uk
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>xlib.fallback occasionally incorrectly treats OVER as SOURCE
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>cairo-bugs@cairographics.org
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>sixtysix@inwind.it
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>xlib backend
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>cairo
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=106329" name="attach_106329" title="quick hack">attachment 106329</a> <a href="attachment.cgi?id=106329&action=edit" title="quick hack">[details]</a></span>
quick hack

the xlib.fallback composer calls a fill_reduces_to_source in
src/cairo.image-compositor.c that simplifies an OVER operator fill
to a SOURCE operator fill whenever the destination is clear.

This means that you have to mark the shm-image-surface as no longer clear
after it is filled as the attached quick hack does.

It fixes    

finer-grained-fallbacks      
over-above-source
over-around-source
over-between-source

all .xlib.fallback.rgb24</pre>
        </div>
      </p>
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